CN112551659A - Method for recovering phosphorus in wastewater by using insoluble magnesium source - Google Patents
Method for recovering phosphorus in wastewater by using insoluble magnesium source Download PDFInfo
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- CN112551659A CN112551659A CN202011305669.3A CN202011305669A CN112551659A CN 112551659 A CN112551659 A CN 112551659A CN 202011305669 A CN202011305669 A CN 202011305669A CN 112551659 A CN112551659 A CN 112551659A
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
- C02F1/5236—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using inorganic agents
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B25/00—Phosphorus; Compounds thereof
- C01B25/16—Oxyacids of phosphorus; Salts thereof
- C01B25/26—Phosphates
- C01B25/45—Phosphates containing plural metal, or metal and ammonium
- C01B25/451—Phosphates containing plural metal, or metal and ammonium containing metal and ammonium
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/10—Inorganic compounds
- C02F2101/105—Phosphorus compounds
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W10/00—Technologies for wastewater treatment
- Y02W10/30—Wastewater or sewage treatment systems using renewable energies
- Y02W10/37—Wastewater or sewage treatment systems using renewable energies using solar energy
Abstract
The invention discloses a method for recovering phosphorus in wastewater by using an insoluble magnesium source, which comprises a pretreatment link and a phosphorus recovery link, wherein the pretreatment link comprises the following steps: (1) establishing a relation between the pH value of the wastewater with different initial phosphorus concentrations and the phosphorus loss rate; (2) correspondingly obtaining the pH value of the wastewater in actual production according to the phosphorus loss rate required by the production; (3) guiding the adding amount of the insoluble magnesium source according to the pH value of the wastewater during actual production; the phosphorus recovery link comprises: and adding a water-soluble magnesium source, an ammonia source and caustic soda flakes into the pretreated wastewater to obtain a struvite particle product. According to the method, the low-cost insoluble magnesium source is used in the pretreatment link of the wastewater generated in the activated carbon production, and the acidity of the wastewater is used for dissolving the insoluble magnesium source, so that the purposes of quantitatively controlling the adding of the insoluble magnesium source in real time and improving the pH value of the wastewater can be simultaneously achieved, and the cost of the whole wastewater treatment process is reduced.
Description
Technical Field
The invention relates to the technical field of sewage treatment and recycling, in particular to a method for recovering phosphorus in wastewater by using an insoluble magnesium source.
Background
The phosphorus concentration in the wastewater from the production of the activated carbon is extremely high, and mainly originates from the rinsing and gas washing processes of the activated carbon. In order to meet the requirement of environmental protection, enterprises need to reduce the phosphorus in the wastewater to a certain concentration by themselves, and then discharge the phosphorus into a sewage pipe network and send the phosphorus to an industrial wastewater treatment plant for advanced treatment. The conventional lime neutralization method can only ensure that the discharged phosphorus reaches the standard, but the sediment is a mixture of calcium phosphate and lime, so that the recycling difficulty is high, and finally the sediment can only be used as solid waste for disposal, which is a huge waste for precious phosphorus resources. Phosphorus is a non-renewable resource, and the dual purposes of phosphorus pollution treatment and resource recovery can be realized by recovering phosphorus from wastewater, so that the environmental protection requirement of enterprises is met, and the obtained phosphorus recovery product can bring economic benefits for the enterprises, and is a treatment method integrating environment and economy.
Researches show that the struvite crystallization method is an efficient phosphorus recovery method, has the characteristics of good removal effect, high reaction rate, simple process and the like, and is particularly suitable for treating high-phosphorus wastewater. However, the cost of the reagent for struvite crystallization is a key factor that prevents its widespread use. With a water-soluble source of magnesium (e.g. MgCl)2、MgSO4Etc.) and the increasing price of alkali (e.g., flake alkali), the operating costs of the traditional struvite process have increased. Domestic and foreign studies have demonstrated the use of insoluble magnesium sources (e.g. MgO, Mg (OH)2、MgCO3Etc.) can effectively reduce the cost of the medicament.
However, the water quality (phosphate concentration) of the wastewater from the activated carbon production fluctuates greatly, and the mismatching between the adding amount of the insoluble magnesium source and the phosphate concentration can cause the unstable operation of the subsequent struvite crystallization system. In addition, excessive magnesium source is added, so that the cost of the medicament is increased, the pH value is excessively increased, phosphate is precipitated, the risk of subsequent pipeline blockage is increased, and the yield of struvite is reduced. In the existing process or method, the adding control of the insoluble magnesium source is more original, the response time is longer, the process condition is difficult to control, the problems of waste of the insoluble magnesium source, incapability of continuous production and higher phosphorus loss rate still exist, and the industrial application is less.
Disclosure of Invention
Aiming at the problems, the invention provides a method for recovering phosphorus in wastewater by using an insoluble magnesium source, which uses the insoluble magnesium source with low cost in the pretreatment link of the wastewater produced by activated carbon, and uses the acidity of the wastewater to dissolve the insoluble magnesium source, so that the purposes of quantitatively controlling the adding of the insoluble magnesium source and improving the pH value of the wastewater in real time can be simultaneously achieved, and the cost of the whole wastewater treatment process is reduced.
In a first aspect, an embodiment of the present invention provides a method for recovering phosphorus from wastewater by using a poorly soluble magnesium source, where the method includes a pretreatment step and a phosphorus recovery step, and the pretreatment step includes:
(1) establishing a relation between the pH value of the wastewater with different initial phosphorus concentrations and the phosphorus loss rate;
(2) correspondingly obtaining the pH value of the wastewater in actual production according to the phosphorus loss rate required by the production;
(3) guiding the adding amount of the insoluble magnesium source according to the pH value of the wastewater during actual production;
the phosphorus recovery link comprises: and adding a water-soluble magnesium source, an ammonia source and caustic soda flakes into the pretreated wastewater to obtain a struvite particle product.
The insoluble magnesium source is selected from MgO, Mg (OH)2、MgCO3One or a combination of two or more of them.
The water soluble magnesium source is selected from MgCl2、MgSO4And bittern.
Optionally, step (1) comprises the steps of:
according to the difference of the initial phosphorus concentration, different partitions are divided into 500-1000mg/L, 1000-1500mg/L, 1500-2000mg/L and more than 2000 mg/L;
adding different amounts of insoluble magnesium sources into the wastewater, and detecting and recording the real-time phosphorus loss rate and the pH value of the wastewater;
and drawing a corresponding curve of the phosphorus loss rate-the pH value of the wastewater, and fitting the curve to obtain a relational expression between the pH values corresponding to the wastewater with different initial phosphorus concentrations and the phosphorus loss rate.
The phosphorus loss rate is calculated according to the following formula:
in the formula, C0Is the initial phosphorus concentration of the wastewater, CPThe phosphorus concentration of the wastewater after the pretreatment is finished.
The pH value of the wastewater is detected in real time by using a pH meter in the pretreatment process.
In the pretreatment process, with the increasing of the adding amount of the insoluble magnesium source, part of phosphorus in the wastewater interacts with the magnesium source to form struvite, but the part of struvite has extremely small particle size and poor quality, and the other part of struvite forms MgHPO4Or Mg3(PO4)2And the like, and the part of phosphorus cannot form struvite, thereby causing the waste of phosphorus. In a word, no matter phosphorus in the wastewater in the pretreatment process forms low-quality struvite or precipitates, the phosphorus in the wastewater is separated from the wastewater in a solid form, cannot enter a subsequent phosphorus recovery link, cannot form a qualified struvite final product with uniform particle size, and belongs to a phosphorus loss part. Moreover, the phosphorus loss part is solid, which easily blocks the pipeline, causing adverse effects. Meanwhile, the indissolvable magnesium source is used as an alkaline compound, so that the pH value of the wastewater is continuously increased. This causes that with the addition of the insoluble magnesium source, the phosphorus loss rate and the pH value of the wastewater form a positive correlation, a corresponding curve of the phosphorus loss rate-the pH value of the wastewater is drawn, and the curve is fitted to obtain a relational expression between the pH value and the phosphorus loss rate corresponding to the wastewater with different initial phosphorus concentrations.
The invention creatively divides the recovery of phosphorus in the wastewater into two parts, the first part adds an insoluble magnesium source into the wastewater to increase the magnesium content in the wastewater and simultaneously improve the pH value of the wastewater, and the second part continues to add a water-soluble magnesium source into the wastewater to increase the magnesium content in the wastewater and simultaneously culture struvite products with uniform granularity. The insoluble magnesium source partially replaces part of the water-soluble magnesium source, so that the dosage of the water-soluble magnesium source and the overall process cost are reduced. Because the insoluble magnesium source is used for the inherent defect (phosphorus loss) of phosphorus-containing wastewater, the traditional process usually adds the insoluble magnesium source according to a small part of experience, the phosphorus loss is not controlled accurately, the whole process flexibility is poor, the adding amount of the insoluble magnesium source cannot be flexibly adjusted according to different actual requirements, an irregular pipeline is blocked, the supply amount of wastewater needs to be increased to break the blockage, the fluctuation of the water inflow rate of the subsequent phosphorus recovery link is large, the adding amount of the water-soluble magnesium source is adjusted according to the water inflow at any time, the process control difficulty is increased, and the granularity uniformity of a struvite product is poor. Aiming at the technical problems, the invention creatively establishes the relation between the phosphorus loss caused by the insoluble magnesium source and the pH value of the wastewater, and realizes the purpose of accurately controlling the adding amount of the insoluble magnesium source and the phosphorus loss rate in real time by taking the pH value which is easy to monitor and control in real time as a response index. Furthermore, the blockage situation of the pipeline can be controlled, predicted and quantified, and a corresponding scheme, such as cleaning the pipeline at regular time during intermittent production, or quantitatively increasing the flow of wastewater and the adding amount of the water-soluble magnesium source, can be adopted conveniently in time or in advance. In addition, the invention can predict the phosphorus loss rate in the production process in advance, and can pre-design the process parameters such as the size of a pipeline, the flow rate, the dosage of the water-soluble magnesium source, the discharge period and the like according to the phosphorus loss rate, so that the controllability of the whole process is stronger and more accurate, and the control of the granularity and the granularity uniformity of the struvite product is facilitated.
Optionally, the relationship between the pH value and the phosphorus loss rate of the wastewater with different initial phosphorus concentrations is as follows:
at 500<C0When the concentration is less than or equal to 1000mg/L, the pH is 0.5183 multiplied by eta +2.8546, and the coefficient R2 is determined to be 0.9977;
at 1000<C0When the concentration is less than or equal to 1500mg/L, the pH value is 0.1425 multiplied by eta +4.8601, and the coefficient R2 is 0.9381;
at 1500<C0When the concentration is less than or equal to 2000mg/L, the pH value is 0.0174 multiplied by eta +5.7775, and the coefficient R2 is 0.9500;
at C0>At 2000mg/L, pH 0.0295 × η +4.9316, the coefficient R2 was determined to be 0.9099.
Optionally, the above relation is obtained by fitting on the basis of performing continuous experiments in the preprocessing step, and the specific experimental method is as follows:
(1) and (3) determining the phosphorus concentration of the influent wastewater as an initial phosphorus concentration, and mixing the initial phosphorus concentration with the molar ratio of Mg to P of 1:1, adding an insoluble magnesium source into the wastewater;
(2) the interval is 2-6 hours, the phosphorus concentration of the inlet water and the outlet water is simultaneously measured, the Mg/P molar ratio of the inlet water and the phosphorus loss rate (eta) are calculated and recorded on the basis of the phosphorus concentration, and the corresponding pH value is detected and recorded by a pH meter;
(3) setting a phosphorus loss rate of 10% as a regulation parameter, reducing the adding amount of the insoluble magnesium source when the phosphorus loss rate is higher than 10%, and increasing the adding amount of the insoluble magnesium source when the phosphorus loss rate is lower than 10%;
(4) repeating the steps (2) - (3);
(5) and (4) counting the obtained data, partitioning according to the phosphorus concentration of the inlet water wastewater, and fitting the corresponding relation between the average phosphorus loss rate and the average pH value under different partitions.
In some embodiments, the phosphorus loss rate is set to 10% as a control parameter, and the adding amount of the insoluble magnesium source in a fixed proportion is increased or decreased.
For example, when the phosphorus loss rate is higher than 10%, the adding amount of the insoluble magnesium source is reduced by 5% each time until the phosphorus loss rate is equal to 10%; alternatively, the amount of the hardly soluble magnesium source to be added is reduced by 10% at a time until the phosphorus loss rate becomes 10%.
For example, when the phosphorus loss rate is less than 10%, the amount of the hardly soluble magnesium source is increased by 5% each time until the phosphorus loss rate becomes 10%; alternatively, the amount of the hardly soluble magnesium source is increased by 10% each time until the phosphorus loss rate becomes 10%.
The inventor adopts a statistical thought according to the characteristic that the phosphorus concentration of the inlet wastewater is constantly changed in the actual production, breaks through the method of fixing certain experimental parameters and calculating other experimental parameters or experimental results in the conventional experiment, is not limited to the influence of single experimental factors on the pH value and the phosphorus loss rate of the wastewater, focuses on the comprehensive influence of a plurality of experimental factors of the whole process, and simultaneously avoids the workload of a large number of orthogonal experiments of a plurality of single factors. The method is fit aiming at the actual production process of wastewater treatment, omits the complicated analysis of a single factor, directly takes the easily-measured phosphorus concentration of the inlet water as the analysis source, integrates the influence of a plurality of process parameters of the whole process, takes the phosphorus loss rate as a regulation and control parameter, is intensively reflected on the relation between the phosphorus loss rate and the pH value of the wastewater, performs experiments from the aspect of statistics, simplifies the experimental process, and the obtained result is more in line with the actual wastewater treatment process.
The inventor finds that the phosphorus loss rate obtained by the experiment and the pH value of the wastewater show a linear relation in a certain range of the initial phosphorus concentration of the wastewater, and therefore, the relation between the phosphorus loss rate and the pH value of the wastewater is obtained according to different ranges of the initial phosphorus concentration of the wastewater.
In the step (2), the phosphorus loss rate required by the production is 0.1-10%, and the phosphorus loss rate is in positive correlation with the adding amount of the insoluble magnesium source, and the adding amount of the insoluble magnesium source can reduce the adding amount of the water-soluble magnesium source and the flake caustic soda in the phosphorus recovery link and reduce the production cost, so that the adding amount of the insoluble magnesium source is balanced between the reasonable phosphorus loss rate and the production cost.
One advantage of the method for recovering phosphorus from wastewater by using an insoluble magnesium source provided by the invention is that the phosphorus loss rate can be preset according to actual needs, and the pH value of wastewater in actual production can be obtained as the preset pH value of wastewater through the relational expression between the pH value and the phosphorus loss rate, so that the adding amount of the insoluble magnesium source can be indirectly determined, and the method is convenient and rapid.
In the step (3), the method for guiding the adding amount of the insoluble magnesium source according to the pH value of the wastewater during actual production includes that in the pretreatment step, the insoluble magnesium source is added to the wastewater, a pH meter is used for monitoring the pH value of the wastewater in real time, and the pH value is compared with the preset pH value of the wastewater, so that the adding amount of the insoluble magnesium source is correspondingly reduced or increased according to the increase or decrease of the real-time pH value.
The method for recovering phosphorus from wastewater by using the insoluble magnesium source does not need to calculate the adding amount of the insoluble magnesium source in advance, does not need to consider the dissolving condition of the insoluble magnesium source in wastewater with different initial phosphorus concentrations, can guide the adding of the insoluble magnesium source by simply monitoring the pH value, has high control accuracy and simple equipment, and is convenient for industrial application and popularization.
The waste water obtained after the pretreatment link is intermediate waste water, the intermediate waste water contains magnesium ions formed after an insoluble magnesium source is dissolved, the phosphorus recovery link uses a fluidized bed to treat the intermediate waste water, and a water-soluble magnesium source, an ammonia source and caustic soda flakes are added to increase the content of the magnesium ions and the ammonium ions and produce the struvite product.
In a second aspect, the invention provides a device for adding a magnesium source with poor solubility, which is used in the method for recovering phosphorus in wastewater by using the magnesium source with poor solubility in the first part, and the device can automatically adjust feeding frequency according to feedback of the pH value of the wastewater after the magnesium source with poor solubility is added, so as to achieve the purpose of adjusting the feeding amount in real time according to water quality characteristics, wherein the feeding is the adding of the magnesium source with poor solubility.
The device comprises a feeding part, a pH feedback control system, a stirring tank and a fluidized bed, wherein the feeding part comprises a first storage tank, a second storage tank and a screw conveying pump, and the first storage tank and the second storage tank are respectively connected with the stirring tank and the fluidized bed through feeding pipelines; a screw of the screw conveying pump penetrates through the bottom of the first storage tank and is used for gradually adding the insoluble magnesium source in the first storage tank into the stirring tank; the water outlet of the stirring tank is connected with the feed inlet of the fluidized bed; and the pH feedback control system is in communication connection with the screw conveying pump and a pH meter positioned in the stirring tank.
The first storage tank is used for storing the insoluble magnesium source, and the second storage tank is used for storing the water solution of the water-soluble magnesium source; the pretreatment step is carried out in a stirring tank, and the phosphorus recovery step is carried out in a fluidized bed.
First storage tank divide into storage area and discharging area, and the storage area is the back taper, and the opening shape is square or circular, and the storage area bottom links to each other with the discharging area top, and the discharging area bottom is equipped with the discharge gate, the screw rod of screw rod delivery pump runs through the discharging area bottom, and the screw rod stretches out from the discharge gate for progressively throw the indissolvable magnesium source of first storage tank inside and get into the stirred tank.
Optionally, the sidewall of the magazine forms an angle of not less than 45 ° and not more than 90 ° with the vertical direction.
Optionally, the screw conveying pump is installed outside the discharging area.
Optionally, the first storage tank further comprises a plurality of rappers, and the rappers are installed on the outer side wall of the storage area and used for shaking the insoluble magnesium source in the first storage tank to avoid hardening.
Optionally, two rappers are respectively installed at the center of the outer side walls of both sides of the storage area, so that the material in the first storage tank is uniformly vibrated.
Optionally, a rubber layer is arranged between the rapper and the side wall of the storage area, the thickness of the rubber layer is 1-5mm, and the rubber layer has a buffering effect on the rapper and protects the first storage tank.
Optionally, the discharge port of the first storage tank is connected to the stirring tank through a first feeding pipeline.
Optionally, a stirring device and a pH meter are arranged inside the stirring tank, a water inlet and a water outlet are respectively arranged on two side wall surfaces of the stirring tank, and the water outlet is connected with a feed inlet of the fluidized bed and used for conveying the pretreated wastewater to the fluidized bed to continue a phosphorus recovery link. The stirring device is only a common device with a stirring function in the market, and the invention is not particularly limited.
Optionally, the second storage tank is connected with the fluidized bed through a second feeding pipeline and a feeding pump, and is used for feeding the stored water-soluble magnesium source into the fluidized bed to react with phosphorus in the wastewater to produce a struvite product.
Optionally, the pH feedback control system comprises a pH controller and a frequency modulator which are connected with each other, the pH controller presets a control program of a corresponding relation between a pH value and the frequency of the screw conveying pump, the pH controller is connected with a pH meter, and the frequency modulator is connected with the screw conveying pump; the pH meter is used for measuring the pH value of the mixed wastewater in the stirring tank and the insoluble magnesium source and transmitting the pH value to the pH controller, and the pH controller adjusts the output frequency of the frequency modulator in real time according to the control program so as to control the feeding rate of the screw conveying pump and realize the real-time linkage control of the pH value of the wastewater and the feeding of the insoluble magnesium source.
The control program presets the pH value of the wastewater, and when the pH value of the wastewater is greater than the preset value, the screw conveying pump reduces or stops feeding of the insoluble magnesium source; when the pH value of the wastewater is less than the preset value, the screw conveying pump starts or increases the feeding of the insoluble magnesium source.
The foregoing description is only an overview of the technical solutions of the present invention, and the embodiments of the present invention are described below in order to make the technical means of the present invention more clearly understood and to make the above and other objects, features, and advantages of the present invention more clearly understandable.
Drawings
Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. Also, like reference numerals are used to refer to like parts throughout the drawings. In the drawings:
FIG. 1 is a schematic diagram of an apparatus for adding a source of insoluble magnesium in an embodiment of the present invention;
FIG. 2 is a side view of a first accumulator tank in an embodiment of the present invention.
In the attached drawing, 1-a first storage tank, 101-a storage area, 102-a discharge area, 103-a discharge port, 104-a cover plate, 2-a second storage tank, 3-a screw rod conveying pump, 301-a screw rod, 4-a vibrator, 5-a buffer rubber layer, 6-a stirring tank, 7-a pH meter, 8-a pH controller, 9-a frequency modulator, 10-a fluidized bed and 1001-a return pipe.
Detailed Description
Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.
In the following description, suffixes such as "module", "component", or "unit" used to denote elements are used only for facilitating the explanation of the present invention, and have no specific meaning in itself. Thus, "module", "component" or "unit" may be used mixedly.
Example 1
The embodiment provides a method for recovering phosphorus in wastewater by using an insoluble magnesium source, and the embodiment treats wood activated carbon production wastewater, the method comprises a pretreatment link and a phosphorus recovery link, wherein the pretreatment link comprises the following steps:
establishing the relationship between the pH value and the phosphorus loss rate of wastewater with different initial phosphorus concentrations:
(1) according to the difference of the initial phosphorus concentration, different partitions are divided into 500-1000mg/L, 1000-1500mg/L, 1500-2000mg/L and more than 2000 mg/L;
(2) adding MgO with different quantities into the wastewater, detecting and recording the real-time phosphorus loss rate and the pH value of the wastewater:
(i) and (3) determining the phosphorus concentration of the influent wastewater as an initial phosphorus concentration, and mixing the initial phosphorus concentration with the molar ratio of Mg to P of 1:1, adding MgO into the wastewater;
(ii) the interval is 2-6 hours, the phosphorus concentration of the inlet water and the outlet water is simultaneously measured, the Mg/P molar ratio of the inlet water and the phosphorus loss rate (eta) are calculated and recorded on the basis of the phosphorus concentration, and the corresponding pH value is detected and recorded by a pH meter;
the phosphorus loss rate is calculated according to the following formula:
in the formula, C0Is the initial phosphorus concentration of the wastewater, CPThe phosphorus concentration of the wastewater after the pretreatment is finished.
The pH value of the wastewater is detected in real time by using a pH meter in the pretreatment process.
(iii) Setting a phosphorus loss rate of 10% as a regulation parameter, reducing the MgO addition amount by 5% each time when the phosphorus loss rate is higher than 10%, and increasing the MgO addition amount by 5% each time when the phosphorus loss rate is lower than 10%;
(iv) repeating steps (ii) - (iii) above;
(iv) counting the obtained data, partitioning according to the phosphorus concentration of the influent wastewater, drawing a corresponding curve of phosphorus loss rate-wastewater pH value, fitting the corresponding relation between the average phosphorus loss rate and the average pH value under different partitions, and fitting the curve to obtain the relation between the pH value corresponding to the wastewater with different initial phosphorus concentrations and the phosphorus loss rate, wherein the relation is as follows:
at 500<C0When the concentration is less than or equal to 1000mg/L, the pH is 0.5183 multiplied by eta +2.8546, and the coefficient R2 is determined to be 0.9977;
at 1000<C0When the concentration is less than or equal to 1500mg/L, the pH value is 0.1425 multiplied by eta +4.8601, and the coefficient R2 is 0.9381;
at 1500<C0When the concentration is less than or equal to 2000mg/L, the pH value is 0.0174 multiplied by eta +5.7775, and the coefficient R2 is 0.9500;
at C0>At 2000mg/L, pH 0.0295 × η +4.9316, coefficient R2 is determined to be 0.9099;
the phosphate concentration of the wastewater (II) is 840mg/L and is in a first interval (500)<C0Not more than 1000mg/L), calculating to obtain the preset wastewater pH value of 8.04 in actual production according to the phosphorus loss rate required by the production is 10 percent and the relation between the corresponding pH value of the wastewater and the phosphorus loss rate is 0.5183 multiplied by eta + 2.8546;
and (III) guiding the addition of MgO according to the pH value of the preset wastewater during actual production: in the pretreatment link, MgO is added into the wastewater, the pH value of the wastewater is monitored in real time by using a pH meter 7, and compared with the preset wastewater pH value, the addition amount of the MgO is correspondingly reduced or increased according to the increase or decrease of the real-time pH value.
The wastewater obtained after the pretreatment link is intermediate wastewater, the intermediate wastewater contains magnesium ions formed after MgO is dissolved, the fluidized bed is used for treating the intermediate wastewater in the phosphorus recovery link, and MgCl is added2Ammonia source and caustic soda flakes, and increase the content of magnesium ions and ammonium ions to produce the struvite product.
MgO added in the pretreatment step and MgCl added in the phosphorus recovery step2Mg sum of (A) and wastewaterThe molar ratio of P in the phosphorus-containing gas is 1.6:1, and the ratio of Mg/P contributed by MgO is 1.11:1, so that 69.4 percent of MgCl can be saved for fluidized bed phosphorus recovery in the subsequent phosphorus recovery link2And 82.2% of the amount of caustic soda flakes.
The embodiment also provides a device for adding the insoluble magnesium source, as shown in fig. 1-2, the method for recovering phosphorus from wastewater by using the insoluble magnesium source is implemented by using the device, the device comprises a feeding part, a pH feedback control system, a stirring tank 6 and a fluidized bed 10, the feeding part comprises a first storage tank 1, a second storage tank 2 and a screw delivery pump 3, and the first storage tank and the second storage tank are respectively connected with the stirring tank and the fluidized bed through feeding pipelines; a screw of the screw conveying pump 3 penetrates through the bottom of the first storage tank 1 and is used for gradually adding MgO in the first storage tank into the stirring tank 6; the water outlet of the stirring tank 6 is connected with the feed inlet of the fluidized bed 10; the pH feedback control system is in communication connection with the screw conveying pump 3 and a pH meter 7 positioned in the stirring tank.
The first storage tank 1 is used for storing MgO, and the second storage tank 2 is used for storing MgCl2An aqueous solution of (a); the pretreatment step is carried out in the stirred tank 6 and the phosphorus recovery step is carried out in the fluidization step 10.
First stock chest 1 divide into storage area 101 and ejection of compact district 102, and the storage area is the back taper, and the opening shape is square, and storage area 101 bottom links to each other with ejection of compact district 102 top, and ejection of compact district bottom is equipped with discharge gate 103, and screw rod 301 of screw rod delivery pump 3 runs through ejection of compact district bottom, and the screw rod stretches out from the discharge gate.
The top of the first storage tank 1 is provided with a cover plate 104, and the angle formed by the side wall of the storage area 101 and the vertical direction is 60 degrees. The screw conveying pump 3 is arranged outside the discharging area.
The first storage tank 1 further comprises two rappers 4, and the rappers 4 are installed in the centers of the outer side walls of the two sides of the storage area 101 and used for vibrating MgO in the first storage tank to avoid hardening. A buffer rubber layer 5 is arranged between the vibrator 4 and the side wall of the storage area, the thickness of the buffer rubber layer is 5mm, the buffer rubber layer has a buffer effect on the vibrator, and the first storage tank is protected.
The discharge port 103 of the first storage tank is connected with the stirring tank 6 through a first feeding pipeline. The stirring tank 6 is internally provided with a stirring device and a pH meter 7, the two side wall surfaces of the stirring tank are respectively provided with a water inlet and a water outlet, and the water outlet is connected with a feed inlet of the fluidized bed 10 and used for conveying the pretreated wastewater to the fluidized bed to continue a phosphorus recovery link.
The second holding tank 2 is connected to the fluidized bed 10 via a second feeding pipe and a feeding pump (not shown) for storing MgCl2The solution is fed into a fluidized bed, reacts with phosphorus in the wastewater to produce struvite products, and the fluidized bed further comprises a return pipe 1001, and struvite is produced in a phosphorus recovery link at a certain return ratio.
The pH feedback control system comprises a pH controller 8 and a frequency modulator 9 which are connected with each other, the pH controller 8 presets a control program of the corresponding relation between the pH value and the frequency of the screw conveying pump 3, the pH controller 8 is connected with a pH meter 7, and the frequency modulator 9 is connected with the screw conveying pump 3; the pH meter 7 is used for measuring the pH value of the mixed wastewater and MgO in the stirring tank 6 and transmitting the pH value to the pH controller, and the pH controller 8 adjusts the output frequency of the frequency modulator 9 in real time according to the control program so as to control the feeding rate of the screw conveying pump 3 and realize the real-time linkage control of the wastewater pH value and the MgO feeding.
Example 2
In this example, the method for recovering phosphorus from wastewater using an insoluble magnesium source and the apparatus for adding an insoluble magnesium source in example 1 were applied to treat wastewater from wood-based activated carbon production, and struvite crystallization was used to remove phosphates from the wastewater.
The phosphate concentration of the wastewater is 1300mg/L and is in the second interval (1000)<C0Less than or equal to 1500mg/L), controlling the phosphorus loss rate to be 5.4 percent, and calculating the operation pH value to be 5.63 according to the relation between the corresponding pH value of the wastewater and the phosphorus loss rate, wherein the pH value is 0.1425 multiplied by eta + 4.8601.
The pH value of the wastewater in the pretreatment link is measured by presetting a control program of the corresponding relation between the pH value and the frequency of the screw conveying pump, and the pH controller adjusts the output frequency of the frequency modulator in real time according to the control program so as to control the feeding rate of the screw conveying pump. Mg (OH) added in the pretreatment link2MgSO added in the phosphorus recovery link4The molar ratio of the total Mg of (A) to P in the wastewater is 1.6:1,at this time by Mg (OH)2The contribution Mg/P is 0.93:1, and 58.1 percent of MgSO (magnesium sulfate) can be saved for fluidized bed phosphorus recovery in the subsequent phosphorus recovery link4And 34.1% of the amount of caustic soda flakes.
Example 3
In this example, the method for recovering phosphorus from wastewater using an insoluble magnesium source and the apparatus for adding an insoluble magnesium source in example 1 were applied to treat wastewater from wood-based activated carbon production, and struvite crystallization was used to remove phosphates from the wastewater.
The phosphate concentration of the wastewater is 1710mg/L and is in a third interval (1500)<C02000mg/L) and the phosphorus loss rate is controlled to 10.0 percent, and the operation pH value is 5.95 according to the calculation of 0.0174 multiplied by eta + 5.7775. And the pH value of the wastewater in the pretreatment link is measured by presetting a control program of the corresponding relation between the pH value and the frequency of the screw conveying pump, and the pH controller adjusts the output frequency of the frequency modulator in real time according to the control program so as to control the feeding rate of the screw conveying pump. MgCO added in the pretreatment step3MgCl added in the process of recovering phosphorus2The molar ratio of the total Mg of (1) to P in the wastewater was 1.6:1, at which point MgCO was passed3Contributes Mg/P of 1.18:1, and can save 73.8 percent of MgCl for fluidized bed phosphorus recovery in the subsequent phosphorus recovery link2And 48.9% of the amount of caustic soda flakes.
Example 4
In this example, the method for recovering phosphorus from wastewater using an insoluble magnesium source and the apparatus for adding an insoluble magnesium source in example 1 were applied to treat wastewater from wood-based activated carbon production, and struvite crystallization was used to remove phosphates from the wastewater.
The phosphate concentration of the wastewater is 2440mg/L and is in the fourth interval (C)0> 2000mg/L), the phosphorus loss rate was controlled to 4.5%, and the operating pH was 5.06 calculated from pH 0.0295 × η + 4.9316. And the pH value of the wastewater in the pretreatment link is measured by presetting a control program of the corresponding relation between the pH value and the frequency of the screw conveying pump, and the pH controller adjusts the output frequency of the frequency modulator in real time according to the control program so as to control the feeding rate of the screw conveying pump. MgO and Mg (OH) added in the pretreatment link2MgCl added in the process of recovering phosphorus2、MgSO4The molar ratio of the total Mg of (1) to P in the wastewater is 1.6:1, in which case MgO, Mg (OH) are passed through2Contributes Mg/P of 0.54:1, and can save MgCl by 33.8 percent for fluidized bed phosphorus recovery in the subsequent phosphorus recovery link2、MgSO4And 27.6% flake caustic usage.
It should be noted that, in this document, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.
The above-mentioned serial numbers of the embodiments of the present invention are merely for description and do not represent the merits of the embodiments.
While the present invention has been described with reference to the embodiments shown in the drawings, the present invention is not limited to the embodiments, which are illustrative and not restrictive, and it will be apparent to those skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (10)
1. The method for recovering phosphorus from wastewater by using the insoluble magnesium source is characterized by comprising a pretreatment link and a phosphorus recovery link, wherein the pretreatment link comprises the following steps:
(1) establishing a relation between the pH value of the wastewater with different initial phosphorus concentrations and the phosphorus loss rate;
(2) correspondingly obtaining the pH value of the wastewater in actual production according to the phosphorus loss rate required by the production;
(3) guiding the adding amount of the insoluble magnesium source according to the pH value of the wastewater during actual production;
the phosphorus recovery link comprises: and adding a water-soluble magnesium source, an ammonia source and caustic soda flakes into the pretreated wastewater to obtain a struvite particle product.
2. The method for recovering phosphorus from wastewater according to claim 1, wherein the step (1) comprises the steps of:
according to the difference of the initial phosphorus concentration, different partitions are divided into 500-1000mg/L, 1000-1500mg/L, 1500-2000mg/L and more than 2000 mg/L;
adding different amounts of insoluble magnesium sources into the wastewater, and detecting and recording the real-time phosphorus loss rate and the pH value of the wastewater;
and drawing a corresponding curve of the phosphorus loss rate-the pH value of the wastewater, and fitting the curve to obtain a relational expression between the pH values corresponding to the wastewater with different initial phosphorus concentrations and the phosphorus loss rate.
3. The method for recovering phosphorus from wastewater as claimed in claim 2, wherein said phosphorus loss rate is calculated according to the following formula:
in the formula, C0Is the initial phosphorus concentration of the wastewater, CPThe phosphorus concentration of the wastewater after the pretreatment is finished;
the pH value of the wastewater is detected in real time by using a pH meter in the pretreatment process.
4. A method for recovering phosphorus from wastewater as claimed in claim 3, wherein the relationship between pH and phosphorus loss for wastewater of different initial phosphorus concentrations is as follows:
at 500<C0When the concentration is less than or equal to 1000mg/L, the pH value is 0.5183 multiplied by eta + 2.8546;
at 1000<C0When the concentration is less than or equal to 1500mg/L, the pH value is 0.1425 multiplied by eta + 4.8601;
at 1500<C0When the concentration is less than or equal to 2000mg/L, the pH value is 0.0174 multiplied by eta + 5.7775;
at C0>At 2000mg/L，pH＝0.0295×η+4.9316。
5. The method for recycling phosphorus in wastewater according to claim 4, wherein the above relation is obtained by fitting on the basis of continuous experiments in the pretreatment process, and the specific experimental method is as follows:
(1) and (3) determining the phosphorus concentration of the influent wastewater as an initial phosphorus concentration, and mixing the initial phosphorus concentration with the molar ratio of Mg to P of 1:1, adding an insoluble magnesium source into the wastewater;
(2) the interval is 2-6 hours, the phosphorus concentration of the inlet water and the outlet water is simultaneously measured, the Mg/P molar ratio of the inlet water and the phosphorus loss rate (eta) are calculated and recorded on the basis of the phosphorus concentration, and the corresponding pH value is detected and recorded by a pH meter;
(3) setting a phosphorus loss rate of 10% as a regulation parameter, reducing the adding amount of the insoluble magnesium source when the phosphorus loss rate is higher than 10%, and increasing the adding amount of the insoluble magnesium source when the phosphorus loss rate is lower than 10%;
(4) repeating the steps (2) - (3);
(5) and (4) counting the obtained data, partitioning according to the phosphorus concentration of the inlet water wastewater, and fitting the corresponding relation between the average phosphorus loss rate and the average pH value under different partitions.
6. The method for recovering phosphorus from wastewater as claimed in claim 1, wherein in the step (2), the production requires a phosphorus loss rate of 0.1 to 10%.
7. The method for recycling phosphorus in wastewater according to claim 1, wherein in the step (3), the method for guiding the adding amount of the magnesium-insoluble source according to the pH value of the wastewater during the actual production comprises the steps of adding the magnesium-insoluble source to the wastewater in the pretreatment step, monitoring the pH value of the wastewater in real time by using a pH meter, comparing with the preset pH value of the wastewater, and correspondingly reducing or increasing the adding amount of the magnesium-insoluble source according to the increase or decrease of the real-time pH value.
8. The method for recovering phosphorus in wastewater according to any one of claims 1 to 7, wherein a device for adding a slightly soluble magnesium source is used in the method for recovering phosphorus in wastewater, the device comprises a feeding part, a pH feedback control system, a stirring tank and a fluidized bed, the feeding part comprises a first storage tank, a second storage tank and a screw delivery pump, and the first storage tank and the second storage tank are respectively connected with the stirring tank and the fluidized bed through feeding pipelines; a screw of the screw conveying pump penetrates through the bottom of the first storage tank and is used for gradually adding the insoluble magnesium source in the first storage tank into the stirring tank; the water outlet of the stirring tank is connected with the feed inlet of the fluidized bed; and the pH feedback control system is in communication connection with the screw conveying pump and a pH meter positioned in the stirring tank.
9. The method for recycling phosphorus in wastewater according to claim 8, wherein the first storage tank is divided into a storage area and a discharge area, the storage area is in an inverted cone shape, the opening is square or circular, the bottom of the storage area is connected with the top of the discharge area, the bottom of the discharge area is provided with a discharge hole, the screw of the screw conveying pump penetrates through the bottom of the discharge area, and the screw extends out of the discharge hole.
10. The method for recovering phosphorus in wastewater according to claim 9, wherein the first storage tank further comprises a plurality of rappers, the rappers are mounted on the outer side wall of the storage area, and a rubber layer is arranged between the rappers and the side wall of the storage area;
the pH feedback control system comprises a pH controller and a frequency modulator which are connected with each other, the pH controller is preset with a control program of the corresponding relation between the pH value and the frequency of the screw conveying pump, the pH controller is connected with a pH meter, and the frequency modulator is connected with the screw conveying pump; the pH meter is used for measuring the pH value of the mixed wastewater in the stirring tank and the insoluble magnesium source and transmitting the pH value to the pH controller, and the pH controller adjusts the output frequency of the frequency modulator in real time according to the control program so as to control the feeding rate of the screw conveying pump and realize the real-time linkage control of the pH value of the wastewater and the feeding of the insoluble magnesium source.
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